It's easy to get mired in the quicksand of "what ifs" when it comes to trying to figure out how the U.S. should deal with the group known as ISIS. Just as it's tempting to reduce all the complexities of foreign policy in that region to a sound bite.

If the last 13 years of war have taught us anything, it's that action and inaction both have consequences. What's needed when it comes to ISIS is a sober look at reality — the risks and the options — alongside clarity of goals and flexibility in strategy.

There is growing consensus that inaction is not an option — that the group once known as the Islamic State in Iraq and Syria, which has since changed its name to simply the Islamic State to underscore its aim of a global caliphate, needs to be stopped in that quest. U.S. military leaders now see this brutal group, which has made rapid territorial and strategic gains while conducting a campaign of terror, forced conversions, barbaric executions and genocidal threats, as a force that could become more dangerous than al Qaida.

America's experience in Iraq, however, gives us pause. There, the United States invaded a country on faulty premises, became mired in nation building and finally left, leaving behind a destabilized, factionalized country and creating an opportunity for ISIS to sweep in from Syria.

Beating back ISIS comes with its own pitfalls. Pushing it out of Iraq would still leave it positioned in Syria, where it could well end up regrouping. Yet eradicating it in Syria as well could likely mean strengthening the hand of another bad player in the region, Syrian dictator Bashar al-Assad. And what's the next potential radical jihadist faction that we might inadvertently empower if ISIS is taken out of the picture?

All this underscores the need for President Barack Obama to pursue the kind of coalition-building that he has so long spoken of, starting with the Middle Eastern states that have a stake in this. Mr. Obama must make it clear the U.S. will protect its national interests, but it will not play policeman on behalf of the region's leaders while allowing them the luxury of casting America as the bad cop.

The same goes domestically. Congress can't take a pass just so Mr. Obama's critics there can dodge responsibility and continue to quarterback foreign policy from the comfort of talk show armchairs. The president needs to make his case, and Congress needs to do due diligence and then perform its constitutional role.

Finally, we need to acknowledge that the Middle East is a place of ever-shifting sands. A solution that makes sense today may well need to be modified or even abandoned a few months or even weeks down the road. We need, especially in Washington, a more nimble mind-set, in which adaptability is not synonymous with failure.

American history — world history, for that matter — is filled with instances of exaggerated threats and manipulated public opinion designed to jump-start wars. But it's also full of genuine villains and grave threats. We dare not shirk in the face of those that loom today.